This invention generally relates to syringe assemblies and, more particularly, to an assembly including a plastic tip cap for sealing off the end of a prefillable syringe.
A variety of syringe assemblies are commercially available. Some syringe assemblies are prefilled with a medicament, while others are supplied empty and are later filled by a medical professional, for example. In either situation, it is typically imperative to maintain sterility of the syringe assembly during shipment, handling and up to the point of actual use. One example arrangement for supplying prefilled syringes includes a rubber cap portion that is received over the end of a glass syringe body. The rubber cap portion is intended to seal the syringe body closed to maintain the prefilled medicament within the syringe until it is desirable to dispense the medicament during an injection. While such rubber cap portions have proven useful, they are not without shortcomings and drawbacks.
One shortcoming of rubber cap portions is that rubber material is relatively difficult to manufacture within tight tolerances. In situations where very specific dimensional constraints exist, rubber cap portions often do not meet the specific requirements. Another problem associated with rubber cap portions is that rubber material is relatively expensive to utilize during a manufacturing process. Further, rubber material may present the possibility of interacting with a medicament stored within a prefilled syringe when the medicament comes in contact with the rubber material.
Therefore, it is desirable to provide an improved syringe assembly having cap portion that avoids the shortcomings and drawbacks of the rubber cap portions described above. This invention meets that need.
In general terms, this invention is a syringe assembly including a plastic cap that closes off one end of a syringe. The plastic cap seals the syringe closed to maintain a prefilled medicament within the syringe while simultaneously maintaining the sterility of the appropriate portions of the syringe.
A plastic cap designed according to this invention includes an end wall having an outer surface and an inner surface with a plug portion extending away from the inner surface. A continuous side wall extends from the end wall in the same direction as the plug portion. The side wall has an outer surface and an inner surface with at least one engaging portion on the inner surface. The engaging portion is biased into sealing engagement with a corresponding portion of a syringe and the plug portion is received into an opening on the syringe when the cap is received on the end of the syringe.
In the preferred embodiment, the engaging portion includes at least one generally annular rib on the inner surface of the side wall. The plug portion maintains the sterility of the opening in the end of the syringe, while the engaging portion maintains the sterility of a coupling portion near the end of the syringe, which preferably is designed to accommodate a conventional hypodermic needle.
The plastic cap of this invention is especially useful with syringe bodies that are made from plastic materials. The engaging portion of the cap preferably has a dimension that cooperates with a corresponding surface on the syringe so that an interference fit is established when the cap is placed on the end of the syringe.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiments. The drawings that accompany the detailed description can be briefly described as follows.